Ejector refrigerant cycle device and control method thereof

ABSTRACT

An ejector refrigerant cycle device includes an ejector that has a nozzle portion for reducing pressure of refrigerant on a downstream side of a radiator to expand the refrigerant, and a refrigerant suction port from which refrigerant is drawn by a high-velocity refrigerant flow jetted from the nozzle portion, an evaporator that evaporates refrigerant and flows out the evaporated refrigerant to the refrigerant suction port, a flow amount changing unit that changes a refrigerant flow amount flowing into the evaporator, and a pressure abnormality detecting portion for detecting a pressure abnormality of a high-pressure refrigerant on an upstream side of the nozzle portion. In the ejector refrigerant cycle device, when the pressure abnormality detecting portion detects the pressure abnormality, the flow amount changing unit makes the refrigerant flow amount flowing into the evaporator larger than that in a normal pressure state of the high-pressure refrigerant.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2005-359093filed on Dec. 13, 2005, the contents of which are incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates to an ejector refrigerant cycle devicehaving an ejector, and a control method of an ejector refrigerant cycledevice.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 6,837,069 (corresponding to JP-A-2004-53028) describes anejector refrigerant cycle device that is so constructed as to avoid anabnormal increase in a high-pressure side refrigerant pressure in orderto secure the reliability of refrigerant piping and functional partswhich receive the high-pressure side refrigerant pressure of the cycle.

In the ejector refrigerant cycle device of U.S. Pat. No. 6,837,069(corresponding to JP-A-2004-53028), a branch point for branching ahigh-pressure refrigerant flow is provided on an upstream side of anozzle portion of an ejector, a bypass passage for relievinghigh-pressure refrigerant to a portion between a downstream side of anevaporator and a refrigerant suction port of the ejector from thisbranch point is provided, and a mechanical control valve that is openedwhen the high-pressure side refrigerant pressure on the upstream side ofthe nozzle portion satisfies a specified pressure condition (forexample, not less than about 10 MPa at a refrigerant temperature of 40°C.) is arranged in this bypass passage.

According to the above-mentioned construction, when the high-pressureside refrigerant pressure satisfies the specified condition, the controlvalve is opened to relieve the high-pressure refrigerant on the upstreamside of the nozzle portion to the position between the downstream sideof an evaporator and the refrigerant suction port via the bypasspassage, thereby an abnormal increase in the high-pressure siderefrigerant pressure of the cycle can be avoided.

However, in the ejector refrigerant cycle device described in U.S. Pat.No. 6,837,069 (corresponding to JP-A-2004-53028), because thehigh-pressure refrigerant is relieved to the downstream side of theevaporator when the high-pressure side refrigerant pressure satisfiesthe specified pressure condition, the pressure of the high-pressure siderefrigerant is applied to the evaporator. For this reason, theevaporator is required to have resistance to the pressure of thehigh-pressure refrigerant, which results in enlarging the size of theevaporator and increasing cost. Accordingly, the size and cost of thewhole ejector refrigerant cycle device are increased.

SUMMARY OF THE INVENTION

In view of the above-mentioned problems, an object of the presentinvention is to provide an ejector refrigerant cycle device which canprevent the pressure of high-pressure side refrigerant from beingapplied to an evaporator, and avoid an abnormal increase in the pressureof the high-pressure side refrigerant.

It is another object of the present invention to provide a controlmethod of an ejector refrigerant cycle device.

According to an aspect of the present invention, an ejector refrigerantcycle device includes a compressor that draws, compresses and dischargesrefrigerant, a radiator that radiates heat of refrigerant dischargedfrom the compressor, and an ejector that has a nozzle portion forreducing pressure of refrigerant on a downstream side of the radiator toexpand the refrigerant, and a refrigerant suction port from whichrefrigerant is drawn by a high-velocity refrigerant flow jetted from thenozzle portion. Here, the ejector mixes refrigerant drawn from therefrigerant suction port and refrigerant jetted from the nozzle portion,and reduces the velocity of the mixed refrigerant so as to increase itspressure. The ejector refrigerant cycle device further includes anevaporator that evaporates refrigerant and flows out the evaporatedrefrigerant to the refrigerant suction port, a flow amount changing unitthat changes a refrigerant flow amount flowing into the evaporator, anda pressure abnormality detecting means that detects a pressureabnormality of a high-pressure side refrigerant on an upstream side ofthe nozzle portion. In the ejector refrigerant cycle device, thecompressor draws refrigerant on a downstream side of the ejector, andthe flow amount changing unit makes the refrigerant flow amount flowinginto the evaporator larger than that in a normal pressure state of thehigh-pressure side refrigerant when the pressure abnormality detectingmeans detects the pressure abnormality.

Because the flow amount changing unit makes the refrigerant flow amountflowing into the evaporator larger than that in the normal pressurestate of the high-pressure side refrigerant when the pressureabnormality detecting means detects the pressure abnormality, the flowamount of suction refrigerant drawn into the refrigerant port isincreased. Here, the normal pressure state of the high-pressurerefrigerant is a state where the pressure abnormality detecting meansdoes not detect a pressure abnormality.

When the flow rate of suction refrigerant drawn into the refrigerantsuction port of the ejector increases, in the velocity energy of thehigh-velocity refrigerant flow jetted from the nozzle portion, theamount of energy consumed to suck refrigerant increases, thereby thevelocity of the high-velocity refrigerant flow decreases.

Further, because the flow rate of suction refrigerant which is slow inthe velocity of flow with respect to the high-velocity refrigerant flowincreases, the velocity of the flow of the mixed refrigerant flowinginto the diffuser portion decreases.

The diffuser portion converts the kinetic energy of the mixedrefrigerant flow to pressure energy to increase the pressure ofrefrigerant. Thus, when the velocity of the mixed refrigerant flowinginto the diffuser portion decreases, the amount of pressure increase ofrefrigerant in the diffuser portion also decreases. With this, thepressure of refrigerant flowing out of the ejector decreases.

For this reason, the pressure of refrigerant flowing out of the ejectorand drawn by the compressor decreases, and the pressure of thehigh-pressure side refrigerant can be decreased in the ejectorrefrigerant cycle device. As a result, the pressure of high-pressureside refrigerant is not applied to the evaporator, and an abnormalincrease in the high-pressure side refrigerant pressure can be avoided.

Further, even when the evaporator refrigerant flow amount increases, apredetermined amount of refrigerant evaporates in the evaporator toexert a heat absorbing action. Thus, the ejector refrigerant cycledevice can perform a cooling operation even at the time of avoiding anabnormal increase in the high-pressure side refrigerant pressure. Here,the refrigerant flow amount in the present invention may be a mass flowrate.

For example, an accumulator for separating refrigerant flowing out ofthe ejector into vapor refrigerant and liquid refrigerant may bearranged in a liquid refrigerant passage such that the liquidrefrigerant flows from the accumulator into the evaporator. In thiscase, the flow amount changing unit is arranged in the liquidrefrigerant passage.

Alternatively, a branch passage may be provided to be branched from apoint between a downstream side of the radiator and an upstream side ofthe nozzle portion, and to be joined to the refrigerant suction port ofthe ejector. In this case, the flow amount changing unit is arranged inthe branch passage.

The pressure abnormality detecting means may be provided such that, whena high-pressure refrigerant pressure on the upstream side of the nozzleportion becomes not less than a predetermined value, the pressureabnormality detecting means detects the pressure abnormality.Alternatively, the pressure abnormality detecting means may be providedsuch that, when the pressure-increase amount per unit time of thehigh-pressure refrigerant on the upstream side of the nozzle portionbecomes not less than a predetermined amount, the pressure abnormalitydetecting means detects the pressure abnormality.

Furthermore, the flow amount changing unit may be a variable throttlemechanism that is constructed to change an area of a refrigerantpassage. In this case, the flow amount changing unit can decompressrefrigerant flowing into the evaporator.

According to another aspect of the present invention, a control methodof an ejector refrigerant cycle device having an ejector includes a stepof detecting a pressure abnormality of a high-pressure side refrigeranton an upstream side of a nozzle portion of the ejector, and a step ofreducing a pressure increasing amount in a diffuser portion of theejector than that in a normal pressure state of the high-pressurerefrigerant. Therefore, when the pressure abnormality is detected, thepressure of high-pressure side refrigerant can be reduced, therebypreventing the pressure of high-pressure side refrigerant from beingapplied to the evaporator, and avoiding an abnormal increase in thepressure of the high-pressure side refrigerant.

For example, the reducing can be performed by increasing a refrigerantamount flowing into the evaporator, which has a refrigerant outletcoupled to the refrigerant suction port of the ejector, to be largerthan that in the normal pressure state of the high-pressure refrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional objects and advantages of the present invention will be morereadily apparent from the following detailed description of preferredembodiments when taken together with the accompanying drawings.

FIG. 1 is a general construction diagram of an ejector refrigerant cycledevice of a first embodiment of the present invention.

FIG. 2 is a flow chart to show the control of a variable throttlemechanism of an air-conditioning control unit of the first embodiment.

FIG. 3 is a general construction diagram of an ejector refrigerant cycledevice of a second embodiment of the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

In this embodiment, refrigerant (e.g., carbon dioxide) in which ahigh-pressure side refrigerant pressure is higher than a supercriticalpressure is used as the refrigerant of an ejector refrigerant cycledevice. Thus, the ejector refrigerant cycle device of this embodimentconstructs a supercritical refrigerant cycle.

First, in an ejector refrigerant cycle device 10, a compressor 11 draws,compresses and discharges refrigerant, and increases the pressure ofrefrigerant to a supercritical pressure in this embodiment. Thiscompressor 11 has a driving force transmitted thereto from a vehiclerunning engine (not shown) via a pulley and a belt, thereby beingrotated and driven. Moreover, in this embodiment, a well-knownswash-plate type variable displacement compressor capable of controllinga discharge volume variably and continuously by a control signal fromthe outside is used as the compressor 11.

Here, the discharge volume means the geometric volume of an operatingspace in which refrigerant is drawn and compressed and, specifically,means the cylinder volume between the top dead center and the bottomdead center of the stroke of a piston in the compressor 11. By changingthe discharge volume, the discharge capacity of the compressor 11 can beadjusted. The changing of the discharge volume of the compressor 11 isperformed by controlling the pressure Pc of a swash plate chamber (notshown) constructed in the compressor 11 so as to change the slant angleof a swash plate and change the stroke of the piston.

The pressure Pc of the swash plate chamber is controlled by-changing aratio of a discharge refrigerant pressure Pd to a suction refrigerantpressure Ps by using an electromagnetic volume control valve 11 a, inthe compressor 11. The electromagnetic volume control valve 11 a isdriven by the output signal of an air-conditioning control unit 20 to bedescribed later. With this, the compressor 11 can change the dischargevolume (displacement) continuously within a range of from nearly 0% to100%.

Moreover, because the compressor 11 can change the discharge volumecontinuously within a range of nearly from 0% to 100%, the compressor 11can be brought to an operating stop state by decreasing the dischargevolume to nearly 0%. Thus, this embodiment adopts a clutch-lessconstruction in which the rotary shaft of the compressor 11 is alwayscoupled to the vehicle running engine via the pulley and the belt.

The variable displacement compressor 11 may be provided such that poweris transmitted from the vehicle running engine to the compressor 11 viaan electromagnetic clutch. Moreover, when a fixed displacementcompressor is used as the compressor 11, it is also recommend that anon-off control of operating the compressor intermittently by anelectromagnetic clutch is performed to control the ratio of the onoperation to the off operation of the compressor. Even in this case, thedischarge volume of refrigerant of the compressor can be effectivelycontrolled.

A radiator 12 is connected to a downstream side of the refrigerant flowof the compressor 11. The radiator 12 is a heat exchanger that exchangesheat between high-pressure refrigerant discharged from the compressor 11and outside air (i.e., air outside a vehicle compartment) blown by ablower fan 12 a, so as to cool the high-pressure refrigerant. The blowerfan 12 a is an electrically operated fan driven by a motor 12 b.Moreover, the motor 12 b is rotated and driven by control voltageoutputted from the air-conditioning control unit 20 (A/C control unit)to be described later.

This embodiment constructs a supercritical refrigerant cycle, sorefrigerant is not condensed in the radiator 12 and radiates heat as itis held in a supercritical pressure state.

An ejector 13 is connected to the downstream side of the refrigerantflow of the radiator 12. The ejector 13 includes: a nozzle portion 13 athat throttles refrigerant flowing from the radiator 12 so as to reducethe pressure of refrigerant and to expand refrigerant in an isentropicmanner; and a refrigerant suction port 13 b that is arranged so as tocommunicate with the jet port of the nozzle portion 13 a and drawsrefrigerant on the downstream side of an evaporator 17 to be describedlater.

Further, the ejector 13 further includes: a mixing portion 13 c that isarranged on the downstream side of the nozzle portion 13 a and therefrigerant suction port 13 b and mixes a high-velocity refrigerant flowfrom the nozzle portion 13 a with suction refrigerant drawn from therefrigerant suction port 13 b; and a diffuser portion 13 d that isarranged on the downstream side of the mixing portion 13 c and reducesthe velocity of the refrigerant flow so as to increase the pressure ofrefrigerant.

This diffuser portion 13 d is formed in a shape to gradually increasethe area of passage of refrigerant and has a function of reducing thevelocity of the refrigerant flow so as to increase the pressure ofrefrigerant, that is, a function of converting the velocity energy ofrefrigerant to pressure energy thereof.

An accumulator 14 is connected to the downstream side of the refrigerantflow of the diffuser portion 13 d of the ejector 13. The accumulator 14is formed in the shape of a tank and is a vapor/liquid separating unit.The accumulator 14 separates refrigerant in a vapor/liquid mixed state,flowed from the diffuser portion 13 d of the ejector 13, intovapor-phase refrigerant and liquid-phase refrigerant by a difference indensity. Thus, the vapor-phase refrigerant is collected on the upperside in the vertical direction of the inner space of a tank part of theaccumulator 14 and the liquid-phase refrigerant is collected in thelower side on the vertical direction.

Further, a vapor-phase refrigerant outlet 14 a is provided in the top oftank-shaped accumulator 14. The vapor-phase refrigerant outlet 14 a isconnected to the refrigerant suction side of the compressor 11. On theother hand, a liquid-phase refrigerant outlet 14 b is provided in thebottom of the tank part of the accumulator 14. The liquid-phaserefrigerant outlet 14 b is connected to a liquid-phase refrigerantpassage 15.

This liquid-phase refrigerant passage 15 is refrigerant piping forconnecting the liquid-phase refrigerant outlet 14 b of the accumulator14 to the refrigerant suction port 13 b of the ejector 13. In theliquid-phase refrigerant passage 15 are arranged a variable throttlemechanism 16 and an evaporator 17. The variable throttle mechanism 16reduces the pressure of liquid-phase refrigerant flowing out of theaccumulator 14 to adjust the evaporation pressure of refrigerant in theevaporator 17. In this embodiment, the variable throttle mechanism 16 isan electric variable throttle mechanism controlled by the control signalof the air-conditioning control unit 20.

For example, the variable throttle mechanism 16 is a flow rate adjustingvalve that includes a valve mechanism 16 a constructed so as to changethe area of passage of refrigerant and a stepping motor 16 b rotated anddriven by a control signal (pulse signal) outputted from theair-conditioning control unit 20. When the stepping motor 16 is rotated,the valve body of the valve mechanism 16 a is displaced to adjust thearea of passage of refrigerant continuously.

Thus, the valve mechanism 16 a of the variable throttle mechanism 16constructs flow amount changing unit for changing an evaporatorrefrigerant flow amount Ge flowing into the evaporator 17, and thestepping motor 16 b constructs drive means for changing the area ofpassage of refrigerant of the valve mechanism 16 a.

The evaporator 17 is a heat exchanger that is arranged on the downstreamside of the refrigerant flow of the variable throttle mechanism 16 inthe liquid-phase refrigerant passage 15 and exchanges heat betweenlow-pressure refrigerant having pressure reduced by the variablethrottle mechanism 16 and air blown by the blower fan 17 a. Thelow-pressure refrigerant in the evaporator 17 absorbs heat from air soas to cool air in a compartment to be cooled.

Moreover, the blower fan 17 a is an electrically operated fan driven bya motor 17 b. The motor 17 b is rotated and driven by control voltageoutputted from the air-conditioning control unit 20 to be describedlater. Further, as described above, the downstream side of theevaporator 17 is connected to the refrigerant suction port 13 b of theejector 13, such that the refrigerant from the evaporator 17 is drawninto the refrigerant suction port 13 b of the ejector 13.

Next, an electric control operation of this embodiment will bedescribed. The air-conditioning control unit 20 is constructed of awell-known microcomputer including a CPU, a ROM, a RAM and the like andits peripheral circuit, and performs various kinds of computations andprocessing on the basis of control programs stored in the ROM to controlthe operations of the above-mentioned various kinds of devices 11 a, 12b, 16 b, 17 b, for example.

Moreover, to the air-conditioning control unit 20, detection signalsfrom a group of various kinds of sensors and various operating signalsfrom operating panel (not shown) are inputted. Specifically, the groupof sensors include a temperature sensor 21 for detecting a refrigeranttemperature Tev on the downstream side of the evaporator 17, a pressuresensor 22 for detecting a refrigerant pressure Pev on the downstreamside of the evaporator 17, and a pressure sensor 23 for detecting arefrigerant pressure Pnoz on the upstream side of the nozzle portion 13a. Moreover, the operating panel is provided with an operating switchfor operating a refrigerating unit and a temperature setting switch forsetting temperature in the compartment to be cooled (e.g., refrigerationcompartment).

Next, operation of the ejector refrigerant cycle device in theabove-mentioned construction will be described. First, when the vehiclerunning engine is operated, a rotational drive force is transmitted fromthe vehicle running engine to the compressor 11. Further, when theoperating signal of the operating switch is inputted to theair-conditioning control unit 20 from the operating panel, an outputsignal is outputted from the air-conditioning control unit 20 to theelectromagnetic volume control valve 11 a on the basis of the previouslystored control program.

The discharge volume (displacement) of the compressor 11 is determinedby this output signal, and the compressor 11 draws vapor-phaserefrigerant from the vapor-phase refrigerant outlet 14 a of theaccumulator 14 and compresses the vapor-phase refrigerant to asupercritical state and then discharges the vapor-phase refrigerant. Therefrigerant in the supercritical state, discharged from the compressor11, flows into the radiator 12 and is cooled by outside air. Further,refrigerant flowing out of the radiator 12 flows into the nozzle portion13 a of the ejector 13.

The refrigerant flowing into the nozzle portion 13 a of the ejector 13has its pressure reduced in the nozzle portion 13 a, thereby beingbrought to a two-phase state of vapor and liquid. The pressure energy ofhigh-pressure refrigerant is converted to velocity energy by the nozzleportion 13 a, thereby refrigerant is brought to a high-velocityrefrigerant flow and is jetted from the jet port of the nozzle portion13 a. Refrigerant on the downstream side of the evaporator 17 is drawnfrom the refrigerant suction port 13 b by a pressure drop produced nearthe jet port of the nozzle portion 13 a at this time.

The refrigerant jetted from the nozzle portion 13 a and the refrigerantdrawn from the refrigerant suction port 13 b are mixed with each otherin the mixing portion 13 c on the downstream side of the nozzle portion13 a, and flows into the diffuser portion 13 d. In this diffuser portion13 d, the velocity energy of the refrigerant is converted to pressureenergy by the area of passage being enlarged, so the pressure of therefrigerant on the downstream side of the ejector 13 is increasedaccording to the velocity of the flow of the refrigerant flowing intothe diffuser portion 13 d.

The refrigerant flowing out of the diffuser portion 13 d of the ejector13 flows into the accumulator 14, and is separated into vapor-phaserefrigerant and liquid-phase refrigerant. The vapor-phase refrigerant inthe accumulator 14 is again drawn into and compressed by the compressor11.

On the other hand, the liquid-phase refrigerant in the accumulator 14flows into the liquid-phase refrigerant passage 15 by the suctionfunction of the ejector 13. This liquid-phase refrigerant has flow-rateadjusted and pressure-reduced by the variable throttle mechanism 16, andflows into the evaporator 17. When the liquid-phase refrigerant isevaporated in the evaporator 17, the liquid-phase refrigerant absorbsheat from air in the refrigeration compartment (i.e., the compartment tobe cooled) blown by the blower fan 17 a, thereby air in therefrigeration compartment is cooled.

The refrigerant flowing out of the evaporator 17 is drawn into therefrigerant suction port 13 b and is mixed with a high-velocityrefrigerant flow jetted from the nozzle portion 13 a.

The air-conditioning control unit 20 in this embodiment controls thestepping motor 16 b of the variable throttle mechanism 16 so as tochange the area of passage of refrigerant of the valve mechanism 16 a.The operation of the air-conditioning control unit 20 will be describedon the basis of a flow chart shown in FIG. 2. First, at step S1, thecontrol signals of a refrigerant temperature Tev on the downstream sideof the evaporator 17, a refrigerant pressure Pev on the downstream sideof the evaporator 17, and a refrigerant pressure Pnoz on the upstreamside of the nozzle portion 13 a are read.

Next, at step 82, it is determined on the basis of Pnoz read at step S1whether or not the high-pressure side refrigerant pressure of the cycleis abnormal. Specifically, it is determined whether or not the detectedrefrigerant pressure Pnoz is not higher than a reference high-pressurerefrigerant pressure KPnoz.

Here, the reference high-pressure refrigerant pressure KPnoz is a valuepreviously set to determine that a high-pressure side refrigerantpressure on the upstream side of the nozzle portion 13 a becomesabnormally high within a range not exceeding the pressure resistancevalue of the refrigerant piping and the functional parts (for example,radiator 12), which receive the high-pressure side refrigerant pressureon the upstream side of the nozzle portion 13 a.

Thus, when it is determined that Pnoz≦Kpnoz at step S2, it is determinedthat the high-pressure side refrigerant pressure of the cycle is not inthe state of abnormal pressure and the control routine proceeds to stepS3. When it is not determined that Pnoz≦KPnoz, it is determined that thehigh-pressure side refrigerant pressure of the cycle is in the state ofabnormal pressure and the control routine proceeds to step S5. For thisreason, in this embodiment, step S2 is a determination means fordetermining whether or not the high-pressure side refrigerant pressureof the cycle is in the state of abnormal pressure on the basis of thedetection value of the pressure sensor 23.

At step S3, a normal operation control is performed because thehigh-pressure side refrigerant pressure is not in the state of abnormalpressure. In this normal operation control, the refrigerant passage areaof the valve mechanism 16 a is controlled in such a way that refrigeranton the downstream side of the evaporator 17 has a set degree ofsuperheat.

For example, the degree of superheat of refrigerant on the downstreamside of the evaporator 17 is computed on the basis of the refrigeranttemperature Tev and the refrigerant pressure Pev which are read at stepS1 by the air-conditioning control unit 20, and a control signal (pulsesignal) is outputted to the stepping motor 16 b so that this degree ofsuperheat approaches to a previously set value.

By controlling the degree of superheat of refrigerant on the downstreamside of the evaporator 17 to a predetermined degree of superheat, whenliquid-phase refrigerant flowing into the evaporator 17 is evaporated,the liquid-phase refrigerant absorbs heat from air blown by the blowerfan 17 to cool the air blown. Therefore, it can prevent the evaporatorrefrigerant flow amount Ge flowing into the evaporator 17 from beingincreased unnecessarily.

For this reason, the flow rate of suction refrigerant drawn into therefrigerant suction port 13 b of the ejector 13 is not increasedunnecessarily either, thereby the velocity of flow of a mixed flowproduced by mixing the suction refrigerant with the high-velocityrefrigerant flow jetted from the nozzle portion 13 a is not reduced. Thevelocity energy of the mixed flow is converted to pressure energy in thediffuser portion 13 d to increase the pressure of refrigerant on thedownstream side of the ejector 13.

Thus, the refrigerant evaporation pressure of the evaporator 17connected to the refrigerant suction port 13 b becomes lower than therefrigerant pressure on the downstream side of the ejector 13. Even whenthe refrigerant evaporation temperature in the evaporator 17 is set to acooling temperature (for example, from −5° C. to 5° C.) suitable forrefrigeration, the pressure of refrigerant drawn by the compressor 11can be made higher than the refrigerant evaporation pressure in theevaporator 17. As a result, the drive power of the compressor 11 can bereduced and the operation efficiency of the cycle can be improved.

When the normal operation control at step S3 is performed, the controlroutine proceeds to step S4 and then after a set time T (e.g., a unittime) elapses, the control routine returns again to step S1.

Next, when it is not determined at step S2 that Pnoz≦KPnoz, it isdetermined that the high-pressure side refrigerant pressure of the cycleis in the state of abnormal pressure and the control routine proceeds tostep S5. At step S5, the air-conditioning control unit 20 outputs acontrol signal (pulse signal) to the stepping motor 16 b so as to expandthe refrigerant passage area of the valve mechanism 16 a by a specifiedvalue and then routine proceeds to step S6.

Next, Pnoz is read again at step S6 and the control routine proceeds tostep S7. At step S7, it is determined whether or not Pnoz is not lessthan the previously set reference high-pressure refrigerant pressureKPnoz—α. Here, α is a predetermined value for setting a hysteresis widthso as to prevent the refrigerant passage area control of the valvemechanism 16 a from hunting.

Specifically, it is determined at step S7 whether or not Pnoz≦KPnoz—α.When it is determined that Pnoz≦KPnoz—α, it is determined that thehigh-pressure side refrigerant pressure becomes out of the state ofabnormal pressure and the control routine proceeds to step S4. That is,when Pnoz≦KPnoz—α at step S7, it is determined that the high-pressureside refrigerant pressure becomes the normal state. On the other hand,when it is not determined that Pnoz≦KPnoz—α, it is determined that thehigh-pressure side 10 refrigerant pressure continues to be in the stateof abnormal pressure, that is, is abnormally high pressure, and thecontrol routine returns to step S5. Thus, the air-conditioning controlunit 20 outputs a control signal (pulse signal) to the stepping motor 16b so as to expand the refrigerant passage area of the valve mechanism 16a.

In this manner, when it is determined that the high-pressure siderefrigerant pressure is in the state of abnormal pressure, theair-conditioning control unit 20 controls the stepping motor 16 b so asto expand the refrigerant passage area of the valve mechanism 16 a. Inthis case, the evaporator refrigerant flow amount Ge flowing into theevaporator 17 is increased. For this reason, the flow rate of suctionrefrigerant drawn into the refrigerant suction port 13 b of the ejector13 is also increased.

Thus, the velocity of flow of the mixed refrigerant produced by the mixof the suction refrigerant flow with the high-velocity refrigerant flowis also decreased so as to reduce also the velocity energy of the mixedrefrigerant flow to be converted to the pressure energy in the diffuserportion 13 d of the ejector 13. In this case, the amount of increase inthe refrigerant pressure in the diffuser portion of the ejector 13 isreduced. As a result, the pressure of refrigerant drawn by thecompressor 11 is reduced as compared with pressure at the time of anormal operation and the pressure of refrigerant discharged from thecompressor 11 is also reduced, thereby an abnormal increase in thehigh-pressure side refrigerant pressure of the cycle can be avoided.

Further, even when the evaporator refrigerant flow amount Ge(refrigerant flow rate) is increased, because a part of liquid-phaserefrigerant flowing into the evaporator 17 from the accumulator 14 isevaporated, this part absorbs heat from air blown from the blower fan 17a and hence can cool the air blown from the air blower fan 17 a. Thatis, the cycle can perform a cooling operation even in this abnormaloperation control.

In this embodiment, in the normal operation control in which a pressureabnormality in the high-pressure side refrigerant pressure of the cycleis not detected, it is possible to reduce the drive force of thecompressor 11 and to improve the operation efficiency of the cycle byincreasing the pressure of refrigerant to be drawn by the compressor 11using the pressure increasing function of the diffuser portion 13 d.

Further, when a pressure abnormality on the high-pressure siderefrigerant pressure of the cycle is detected, the evaporatorrefrigerant flow amount Ge (refrigerant flow rate) is increased and theabnormal operation control is performed. Accordingly, in the abnormaloperation control, it is possible to suppress the refrigerant pressureincrease in the diffuser portion 13 d while performing the coolingoperation of the cycle, and to avoid the abnormally high pressure of thecycle. Therefore, in the ejector refrigerant cycle device of thisembodiment, the cooling operation can be performed without applying thepressure of high-pressure side refrigerant to the evaporator 12.

Second Embodiment

In the above-described first embodiment, refrigerant cycle is providedwith the liquid-phase refrigerant passage 15 for connecting theliquid-phase refrigerant outlet 14 b of the accumulator 14 to therefrigerant suction port 13 b of the ejector 13, and the variablethrottle mechanism 16 and the evaporator 17 are arranged in thisliquid-phase refrigerant passage 15. In the second embodiment, however,as shown in FIG. 3, the liquid-phase refrigerant passage 15 is notprovided but there is provided a branch passage 25 for branching therefrigerant flow at a branch point Z that is positioned between thedownstream side of the radiator 12 and the upstream side of the nozzleportion 13 a of the ejector 13.

This branch passage 25 is a refrigerant passage for connecting thebranch point Z to the refrigerant suction port 13 b of the ejector 13.In this embodiment, the variable throttle mechanism 16 is arranged inthe branch passage 25, and the evaporator 17 is arranged on thedownstream side of the refrigerant flow of the variable throttlemechanism 16 in the branch passage 25. The variable throttle mechanism16 and the evaporator 17 have structures, respectively, similar to thosedescribed in the first embodiment. Here, in this embodiment, in order toavoid confusion with a second evaporator 26 to be described later, theevaporator 17 is referred to as a first evaporator in the followingdescription.

Moreover, in this embodiment, the second evaporator 26 is arrangedbetween the downstream side of the ejector 13 and the accumulator 14.The second evaporator 26 is a heat exchanger that exchanges heat betweenlow-pressure refrigerant on the downstream side of the ejector 13 andair in the refrigeration compartment (compartment to be cooled), blownfrom the blower fan 17 a, to make the low-pressure refrigerant absorbheat to cool air in the refrigeration compartment.

Further, in this embodiment, the pressure sensor 23 for detecting therefrigerant pressure Pnoz on the upstream side of the nozzle portion 13a is arranged on the upstream side of the branch point Z. Of course, theposition of the pressure sensor 23 is not limited to this position, butfor example, may be arranged between the branch point Z and the nozzleportion 13 a. In the second embodiment, the other structures of theejector refrigerant cycle device can be made similar to those of theabove-described first embodiment.

Next, the operation of the ejector refrigerant cycle device according tothis embodiment will be described. First, when the vehicle runningengine is operated, just as in the first embodiment, refrigerant in asupercritical state flows from the compressor 11 into the condenser 12,thereby being cooled by the outside air.

Further, refrigerant flowing out from the radiator 12 is branched at thebranch point Z into a refrigerant flow flowing into the nozzle portion13 a of the ejector 13 and a refrigerant flow flowing into the branchpassage 25. Thus, in this embodiment, the flow rate of the refrigerantflowing into the branch passage 25 becomes the evaporator refrigerantflow amount Ge.

The refrigerant flowing into the nozzle portion 13, just as in the firstembodiment, is pressure-reduced in the nozzle portion 13 a and drawsrefrigerant on the downstream side of the first evaporator 17 from therefrigerant suction port 13 b. Further, refrigerant jetted from thenozzle portion 13 a and refrigerant drawn from the refrigerant suctionport 13 b are mixed with each other in the mixing portion 13 c and ispressure-increased in the diffuser portion 13 d according to thevelocity energy of the mixed refrigerant flow.

Refrigerant flowing out from the diffuser portion 13 d flows into thesecond evaporator 26. In the second evaporator 26, the low-pressurerefrigerant having pressure-reduced in the nozzle portion 13 a absorbsheat from air blown from the blower fan 17 a and evaporates. Therefrigerant after having passed through the second evaporator 26 flowsinto the accumulator 14 and is separated into vapor-phase refrigerantand liquid-phase refrigerant. The vapor-phase refrigerant in theaccumulator 14 is drawn and compressed again by the compressor 11.

On the other hand, the refrigerant flowing into the branch passage 25 isflow-rate adjusted and pressure-reduced by the variable throttlemechanism 16 and flows into the first evaporator 17. In the firstevaporator 17, the low-pressure refrigerant flowing therein absorbs heatfrom air flowing from the second evaporator 26 and evaporates. Withthis, air blown by the blower fan 17 a and cooled by the secondevaporator 26 is further cooled in the first evaporator 17. Therefrigerant on the downstream side of the first evaporator 17 is drawninto the refrigerant suction port 13 b and is mixed with high-velocityrefrigerant flow from the nozzle portion 13 a.

Also in the above-mentioned construction, the degree of throttle openingof the variable throttle mechanism 16 can be controlled as shown by theflow chart in FIG. 2, just as in the first embodiment. That is, in thenormal operation control in which a pressure abnormality in thehigh-pressure side refrigerant pressure of the cycle is not detected, itis possible to reduce the drive force of the compressor 11 and toimprove the operation efficiency of the cycle by increasing the pressureof refrigerant to be drawn by the compressor 11, by using the pressureincrease of refrigerant in the diffuser portion 13 d.

Further, when a pressure abnormality in the high-pressure siderefrigerant pressure of the cycle is detected, the evaporatorrefrigerant flow amount Ge is increased. Accordingly, it is possible tosuppress the pressure increase of refrigerant in the diffuser portion 13d, thereby preventing an abnormal high pressure of the cycle whileperforming the cooling operation of the cycle. Therefore, a highpressure is not applied to the first evaporator 17.

Still further, in this embodiment, because the refrigerant flow isbranched at the branch point Z on the upstream side of the nozzleportion 13 a, the variable throttle mechanism 16 increases theevaporation refrigerant flow amount Ge and at the same time reduces theflow rate of the refrigerant flowing into the nozzle portion 13 a. As aresult, the velocity of the mixed refrigerant flowing into the diffuserportion 13 d is reduced, thereby reducing the amount of pressureincrease in the refrigerant in the diffuser portion 13 d.

Other Embodiment

The present invention is not limited to the above-mentioned embodimentsbut can be modified variously as described below.

(1) In the above-mentioned embodiments, the electric variable throttlemechanism is used as the variable throttle mechanism 16 that has theflow rate adjustment function, but a mechanical variable throttlemechanism also can be employed as the variable throttle mechanism 16having the flow rate adjustment function.

For example, a pressure responding means displaced in response to thehigh-pressure side refrigerant on the upstream side of the nozzleportion 13 a may be provided. In this case, the pressure respondingmeans is constructed of a diaphragm or a bellows. Furthermore, a load isapplied to the pressure responding means by elastic means such as a coilspring from a direction opposite to the force that the pressureresponding means receives from the high-pressure refrigerant pressure.With this, pressure abnormality detecting means can be constructed suchthat, when the high-pressure refrigerant pressure becomes not less thana predetermined value determined by the elastic means, the pressureresponding means is displaced.

Further, a valve mechanism of the flow amount changing unit for changingthe evaporator refrigerant flow amount Ge can be combined with thevariable throttle mechanism so as to expand the refrigerant passage areaaccording to the amount of displacement of this pressure respondingmeans. This construction can mechanically construct the variablethrottle mechanism (flow amount changing unit) that increases theevaporator refrigerant flow amount Ge when the high-pressure siderefrigerant pressure increases.

(2) In the above-mentioned embodiment, at step S2 of the control programexecuted by the air-conditioning control unit 20, a pressure abnormalityis detected when the refrigerant pressure Pnoz on the upstream side ofthe nozzle 13 a is larger than the reference high-pressure refrigerantpressure KNnoz. However, a pressure abnormality may be detected on thebasis of the amount of increase per unit time in the refrigerantpressure Pnoz on the upstream side of the nozzle portion 13 a.

For example, the discharge side refrigerant pressure of the compressor12 may be abruptly increased by an abrupt increase in the number ofrevolutions of the compressor 11, even if the actual refrigerantpressure on the upstream side of the nozzle portion 13 a is notincreased to the reference high-pressure refrigerant pressure Kpnoz.Even in this case, a pressure abnormality can be actually detected onthe basis of the amount of increase per unit time in Pnoz. With this, itis possible to more surely ensure the reliability of the refrigerantpiping and the functional parts.

(3) In the above-mentioned second embodiment, the first and secondevaporators 17, 26 cool the same compartment to be cooled (e.g., air inthe refrigeration compartment). However, the first and secondevaporators 17, 26 may cool different objects or spaces to be cooled.

For example, it is possible to use the first evaporator 17 for coolingair in the compartment of a refrigerator for a vehicle and to use thesecond evaporator 26 for cooling air in a passenger compartment of thevehicle. In this case, since the outlet side of the first evaporator 17is connected to the refrigerant suction port 13 b of the ejector 13, itis possible to apply the lowest pressure immediately after reducingpressure in the nozzle portion 13 a to the outlet side of the firstevaporator 17 and to apply pressure after being increased in thediffuser portion 14 b as the refrigerant pressure of the secondevaporator 26.

With this, the refrigerant evaporation pressure (refrigerant evaporationtemperature) of the first evaporator 17 can be made lower than therefrigerant evaporation pressure (refrigerant evaporation temperature)of the second evaporator 26. Thus, it is possible to perform a coolingoperation in a relatively high temperature range suitable for coolingthe passenger compartment by the second evaporator 26, and at the sametime to perform a cooling operation in a further lower temperature rangesuitable for cooling the refrigerator by the first evaporator 17.

Even when the second evaporator 26 is arranged on the downstream side ofthe diffuser portion 13 d of the ejector 13 in the first embodiment, itis possible to produce the effect described in the first embodiment.

(4) In the above-mentioned embodiments, the first evaporator 17 and thesecond evaporator 26 are used as use-side heat exchangers for coolingair in the refrigeration compartment, which is the compartment to becooled, while the radiator 12 is as a heat exchanger for radiating heatto the atmosphere. On the contrary to this, the present invention may beapplied to a construction (heat pump cycle) having the first evaporator17 and the second evaporator 26 as heat exchangers for absorbing heatfrom a heat source such as the atmosphere, and having the radiator 12 asa use-side heat exchanger for heating air or water which is an object tobe heated.

In other words, the refrigeration cycle according to the embodiments maybe used as a heat pump cycle that constructs the radiator 12 as ause-side heat exchanger (e.g., heater).

(5) In the above-mentioned embodiments, there may be provided an innerheat exchanger for exchanging heat between high-pressure refrigerant onthe downstream side of the radiator 12 and low-pressure refrigerant onthe suction side of the compressor 11. According to this construction,refrigerant on the downstream side of the radiator 12 is cooled, so itis possible to increase a difference in enthalpy (cooling capacity) ofrefrigerant between the refrigerant inlet and outlet in each of thefirst evaporator 17 and the second evaporator 26.

(6) In the above-mentioned embodiments has been described an example ofusing carbon dioxide as refrigerant and constructing a supercriticalrefrigerant cycle in which high-pressure side refrigerant pressureexceeds a supercritical pressure. However, fron-based or HC-basedrefrigerant may be used as the refrigerant. Further, the presentinvention may be applied also to a case of constructing a vaporcompression type subcritical refrigerant cycle in which high pressuredoes not exceed a supercritical pressure.

(7) In the above-mentioned embodiments, a fixed nozzle having a constantrefrigerant passage area has been shown as an example of the nozzleportion 13 a. However, a variable ejector having a variable nozzleportion capable of adjusting the refrigerant passage area may be used asthe ejector 13. As an example, the variable nozzle portion can beemployed, for example, a mechanism in which the position of a needleinserted into the passage of the variable nozzle portion is controlledby an electric actuator to adjust the refrigerant passage area.

Such changes and modifications are to be understood as being within thescope of the present invention as defined by the appended claims.

1. An ejector refrigerant cycle device comprising: a compressor thatdraws, compresses and discharges refrigerant; a radiator that radiatesheat of refrigerant discharged from the compressor; an ejector that hasa nozzle portion for reducing pressure of refrigerant on a downstreamside of the radiator to expand the refrigerant, and a refrigerantsuction port from which refrigerant is drawn by a high-velocityrefrigerant flow jetted from the nozzle portion, wherein the ejectormixes refrigerant drawn from the refrigerant suction port andrefrigerant jetted from the nozzle portion, and reduces the velocity ofthe mixed refrigerant so as to increase its pressure; an evaporator thatevaporates refrigerant and flows out the evaporated refrigerant to therefrigerant suction port; a flow amount changing unit that changes arefrigerant flow amount flowing into the evaporator; and a pressureabnormality detecting means that detects a pressure abnormality of ahigh-pressure refrigerant on an upstream side of the nozzle portion,wherein the compressor draws refrigerant on a downstream side of theejector, and wherein when the pressure abnormality detecting meansdetects the pressure abnormality, the flow amount changing unit makesthe refrigerant flow amount flowing into the evaporator larger than thatin a normal pressure state of the high-pressure refrigerant.
 2. Theejector refrigerant cycle device as in claim 1, further comprising: anaccumulator that separates refrigerant flowing out of the ejector intovapor refrigerant and liquid refrigerant; and a liquid refrigerantpassage through which the liquid refrigerant flows from the accumulatorinto the evaporator, wherein the flow amount changing unit is arrangedin the liquid refrigerant passage.
 3. The ejector refrigerant cycledevice as in claim 1, further comprising: a branch passage branched froma point between a downstream side of the radiator and an upstream sideof the nozzle portion, and is joined to the refrigerant suction port ofthe ejector, wherein the flow amount changing unit is arranged in thebranch passage.
 4. The ejector refrigerant cycle device as in claim 1,wherein when a high-pressure refrigerant pressure on the upstream sideof the nozzle portion becomes not less than a predetermined value, thepressure abnormality detecting means detects the pressure abnormality.5. The ejector refrigerant cycle device as in claim 1, wherein when apressure-increase amount per unit time of the high-pressure refrigeranton the upstream side of the nozzle portion becomes not less than apredetermined amount, the pressure abnormality detecting means detectsthe pressure abnormality.
 6. The ejector refrigerant cycle device as inclaim 1, wherein the flow amount changing unit is a variable throttlemechanism that is constructed to change an area of a refrigerantpassage.
 7. The ejector refrigerant cycle device as in claim 1, furthercomprising: a drive member that drives the flow amount changing unit tochange a refrigerant passage area in the flow amount changing unit; anda control unit that controls operation of the drive member, wherein thepressure abnormality detecting means includes a pressure sensor fordetecting a pressure of high-pressure refrigerant on the upstream sideof the nozzle portion, and determination means that determines whetheror not a detection value of the pressure sensor corresponds to thepressure abnormality, and wherein when the determination meansdetermines that the detection value of the pressure sensor correspondsto the pressure abnormality, the control unit controls the drive memberso as to expand the refrigerant passage area.
 8. The ejector refrigerantcycle device as in claim 1, wherein the ejector further includes amixing portion in which the refrigerant jetted from the nozzle portionand the refrigerant drawn from the refrigerant suction port are mixed,and a diffuser portion which increases pressure of the mixed refrigerantfrom the mixing portion, the device further comprising reducing meansfor reducing a pressure increasing amount of the mixed refrigerant inthe diffuser portion, wherein when the pressure abnormality detectingmeans detects the pressure abnormality, the reducing means reduces thepressure increasing amount of the mixed refrigerant in the diffuserportion than that in the normal pressure state of the high-pressurerefrigerant.
 9. The ejector refrigerant cycle device as in claim 8,wherein the flow amount changing unit is used as the reducing means. 10.The ejector refrigerant cycle device according to claim 3, furthercomprising an another evaporator for evaporating refrigerant flowing outof an outlet port of the ejector.
 11. An ejector refrigerant cycledevice comprising: a compressor that draws, compresses and dischargesrefrigerant; a radiator that radiates heat of refrigerant dischargedfrom the compressor; an ejector that has a nozzle portion for reducingpressure of refrigerant on a downstream side of the radiator to expandthe refrigerant, a refrigerant suction port from which refrigerant isdrawn by a high-velocity refrigerant flow jetted from the nozzleportion, a mixing portion in which the refrigerant jetted from thenozzle portion and the refrigerant drawn from the refrigerant suctionport are mixed, and a diffuser portion which increases pressure of themixed refrigerant from the mixing portion; an evaporator that evaporatesrefrigerant and flows out the evaporated refrigerant to the refrigerantsuction port; a pressure abnormality detecting means that detects apressure abnormality of a high-pressure refrigerant on an upstream sideof the nozzle portion; and reducing means for reducing a pressureincreasing amount of the mixed refrigerant in the diffuser portion ofthe ejector, wherein the compressor draws refrigerant on a downstreamside of the ejector, and wherein when the pressure abnormality detectingmeans detects the pressure abnormality, the reducing means reduces apressure increasing amount of the mixed refrigerant in the diffuserportion than that in a normal pressure state of the high-pressurerefrigerant.
 12. The ejector refrigerant cycle device according to claim11, wherein the pressure abnormality detecting means detects thepressure abnormality when the pressure of refrigerant at the upstreamside of the nozzle portion is higher than a predetermined amount.
 13. Acontrol method of an ejector refrigerant cycle device having an ejectorthat includes a nozzle portion for reducing pressure of a high-pressurerefrigerant, a refrigerant suction port from which refrigerant from anevaporator is drawn by a high-velocity refrigerant flow jetted from thenozzle portion, a mixing portion in which the refrigerant jetted fromthe nozzle portion and the refrigerant drawn from the refrigerantsuction port are mixed, and a diffuser portion which increases pressureof the mixed refrigerant from the mixing portion, the control methodcomprising: detecting a pressure abnormality of the high-pressurerefrigerant on an upstream side of the nozzle portion; and reducing apressure increasing amount of the mixed refrigerant in the diffuserportion than that in a normal pressure state of the high-pressurerefrigerant.
 14. The control method according to claim 13, wherein thereducing is performed by increasing a refrigerant amount flowing intothe evaporator, which has a refrigerant outlet coupled to therefrigerant suction port of the ejector, to be larger than that in thenormal pressure state of the high-pressure refrigerant.